Mechanisms of the energy transfer across the magnetic field by Alfven waves in toroidal plasmas

Physics of the transverse energy transfer by Alfven waves in toroidal plasmas is elucidated. It is found that, in contrast to the classical Alfven waves in infinite plasmas, the Alfven waves in toroidal systems produce plasma compression due to coupling with fast magnetoacoustic waves, which provides the energy transfer. The radial group velocities of the traveling waves constituting the Global Alfven Eigenmodes and Toroidicity-induced Alfven Eigenmodes are calculated. It is shown that equations for Alfven eigenmodes derived in the approximation of vanishing wave field along the equilibrium magnetic field reproduce the longitudinal magnetic field of the wave and lead to correct transverse energy flux. The obtained results explain how Alfven eigenmodes can provide the spatial energy channeling-the transfer of the energy by these modes from the unstable plasma region to the region where the mode damping dominates. Published by AIP Publishing.